As easily as a thermometer tells you the temperature, KeyOmeter automatically detects and displays the musical key. KeyOmeter operates in the "circle of fifths" - a visual representation of the 12 tones of the Western chromatic scale. The outer circle displays the twelve major keys, the inner circle shows their relative minors. Tap the screen to display the name of the key. KeyOmeter works on live music picked up the device's microphone as well and on songs from your iTunes music library.